JP2013087679A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size, by maximally preventing exhaust gas of flowing in a bypass passage from being cooled by a heat exchanger at the low temperature.SOLUTION: This EGR cooler 1 includes the heat exchanger 3 arranged in a casing 2 and cooling the exhaust gas, the bypass passage 5 arranged in the casing and bypassing the heat exchanger, and a flow passage switching valve 9 for supplying the exhaust gas to any one of the heat exchanger and the bypass passage. The heat exchanger 3 has a gas passage 6 for making the exhaust gas flow and a cooling passage 7 for cooling the exhaust gas flowing in the gas passage. The bypass passage 5 is formed in a hollow shaft 4 arranged in the casing 2, the gas passage 6 is arranged outside the hollow shaft 4, and the cooling passage 7 is arranged outside the gas passage.

Description

  The present invention relates to an EGR (Exhaust Gas Recirculation) cooler, and more particularly to an EGR cooler including a heat exchanger for cooling exhaust gas and a bypass passage that bypasses the heat exchanger.

Conventionally, as an EGR cooler, a heat exchanger that is provided in a casing and cools exhaust gas, a bypass passage that is provided in the casing and bypasses the heat exchanger, and an exhaust gas that passes through the heat exchanger and bypass passage And the heat exchanger further includes a gas passage for circulating the exhaust gas and a cooling passage for cooling the exhaust gas flowing through the gas passage. One is known (Patent Document 1).
In this type of EGR cooler, when the exhaust gas is at a high temperature, the exhaust gas is passed through the heat exchanger to lower the temperature. On the other hand, when the exhaust gas is at a low temperature, the exhaust gas is passed through the bypass passage to be cooled. I'm trying not to get it.

Japanese Patent No. 4431579

In general, the EGR cooler is desired to be manufactured as small as possible. However, in order to manufacture the EGR cooler as small as possible, it is necessary to arrange the heat exchanger and the bypass passage as close as possible.
However, if the heat exchanger and the bypass passage are arranged as close as possible, the exhaust gas flowing through the bypass passage is likely to be cooled by the heat exchanger at a low temperature, which is not desirable.
In view of such circumstances, the present invention provides an EGR cooler that can be downsized while preventing the exhaust gas flowing through the bypass passage at low temperatures from being cooled by the heat exchanger as much as possible. To do.

That is, the present invention provides a heat exchanger that is provided in a casing and cools exhaust gas, a bypass passage that is provided in the casing and bypasses the heat exchanger, and an exhaust gas that passes through the heat exchanger and bypass passage. The EGR further includes a gas passage through which the exhaust gas flows and a cooling passage that cools the exhaust gas flowing through the gas passage. In the cooler
A hollow shaft is provided in the casing, the inside of the hollow shaft is used as the bypass passage, the gas passage of the heat exchanger is disposed outside the hollow shaft, and the cooling passage is disposed outside the gas passage. It is characterized by this.

According to the above configuration, since the gas passage of the heat exchanger is disposed outside the hollow shaft serving as the bypass passage and the cooling passage is disposed outside the gas passage, the bypass passage and the cooling passage are connected to the gas passage. Therefore, it is possible to prevent the exhaust gas flowing through the bypass passage at a low temperature from being cooled by the cooling water flowing through the cooling passage as much as possible.
And by the structure which arrange | positions a bypass channel in a heat exchanger, it becomes possible to manufacture an EGR cooler compactly compared with the past.

Sectional drawing which shows 1st Example of this invention. Sectional drawing which shows a state different from FIG. Sectional drawing which follows the III-III line of FIG. Sectional drawing which shows 2nd Example of this invention.

Hereinafter, the present invention will be described with reference to the illustrated embodiment. In FIG. 1, an EGR cooler 1 is provided in a cylindrical casing 2 and provided in a central portion in the casing 2. And a hollow shaft 4 penetrating through the heat exchanger 3. The hollow shaft 4 serves as an exhaust gas bypass passage 5.
The heat exchanger 3 is provided between the inner peripheral surface of the casing 2 and the outer peripheral surface of the hollow shaft 4, and as will be described in detail later, an exhaust gas passage 6 disposed outside the hollow shaft 4, And a cooling passage 7 disposed on the outer side of the gas passage 6.
The exhaust gas flowing in from the inlet port 8 of the EGR cooler 1 is sent to either the bypass passage 5 or the gas passage 6 of the heat exchanger 3 by a flow path switching valve 9 provided on the outlet side of the EGR cooler 1. It is designed to be distributed (see FIGS. 1 and 2).

The casing 2 of the EGR cooler 1 includes a large-diameter cylindrical member 2a and closing members 2b and 2c that are connected to both ends thereof and close each opening, and are located on the left side that becomes the exhaust gas inlet side. The right end portion of the L-shaped inlet cylindrical member 2d is passed through and fixed to the shaft portion of the closing member 2b.
On the other hand, the left end portion of the outlet cylindrical member 2e is fixed to the shaft portion of the right closing member 2c on the exhaust gas outlet side. In this embodiment, the right end portion of the outlet cylindrical member 2e is fixed. The flow path switching valve 9 is integrally connected.
The inlet side of the inlet cylindrical member 2d is formed as the inlet port 8 described above, and the exhaust gas flowing in from the inlet port 8 is divided into two at the outlet of the inlet cylindrical member 2d located in the casing 2. The flow is divided and one flows into the bypass passage 5 and the other flows into the gas passage 6 of the heat exchanger 3.

The heat exchanger 3 has a configuration in which four units 1U to 4U having substantially the same configuration in the present embodiment are connected in the axial direction, and the inside of each unit 1U to 4U and the hollow shaft 4 A space between the outside and the outside of each of the units 1U to 4U and the inside of the casing 2 is a cooling passage 7 while the space between the outside and the casing 2 is inside.
Each of the units 1U to 4U includes a cylindrical large-diameter cylindrical portion 12, a wall portion 13 integrally connected to the right side of each large-diameter cylindrical portion 12 and extending radially inward, And a small-diameter cylindrical portion 14 extending axially rightward from the inside.
Further, a wall portion 15 extending radially inward is provided on the left side of each large-diameter cylindrical portion 12, and a small-diameter cylindrical portion 16 extending axially leftward is integrally provided inside each wall portion 15. Has been.
The inner diameter of the small-diameter cylindrical portion 16 extending to the left side in the axial direction is larger than the outer diameter of the hollow shaft 4 and is fitted inside the small-diameter cylindrical portion 14 extending to the right side of the adjacent unit. By being connected, the units 1U to 4U are integrally connected in the axial direction.

At this time, the small-diameter cylindrical portion 16 projecting to the left side in the first unit 1U located on the leftmost side is fitted on the outer periphery of the left end portion of the inlet cylindrical member 2d and is integrally connected thereto.
On the other hand, the small-diameter cylindrical portion 14 protruding to the right side in the fourth unit 4U located on the rightmost side is configured integrally with the outlet cylindrical member 2e in this embodiment. The small-diameter cylindrical portion 14 may be configured separately from the outlet cylindrical member 2e, and the small-diameter cylindrical portion 14 may be connected and fixed to the outlet cylindrical member 2e. If it does in this way, all the structures of four units 1U-4U can be made the same structure.

Furthermore, each unit 1U-4U is connected with the small diameter cylindrical connection part 20 fitted by the outer periphery of the hollow shaft 4 which comprises the bypass channel 5, and the center part of this connection part 20, and is extended to radial direction outward. And a ring-shaped plate 21. The outer peripheral part of each plate 21 is located in the center of the left and right wall parts 13 and 15 in each unit 1U-4U, the outer diameter is larger than the internal diameter of the small diameter cylindrical parts 14 and 16, and is a large diameter cylindrical shape. It is smaller than the inner diameter of the portion 12.
The outer diameter of the small-diameter cylindrical connecting portion 20 fitted on the outer periphery of the hollow shaft 4 is smaller than the inner diameter of the small-diameter cylindrical portions 14 and 16. The gas passage 6 can be formed between the peripheral surface and the outer peripheral surface of the cylindrical connecting portion 20.

Therefore, as shown in FIG. 2, the exhaust gas flowing into the left small-diameter cylindrical portion 16 flows in the small-diameter cylindrical portion 16 in the axial direction and then flows between the left wall portion 15 and the plate 21. When the fluid flows radially outward and then flows axially between the inner peripheral surface of the large-diameter cylindrical portion 12 and the outer peripheral surface of the plate 21, the space between the right wall portion 13 and the plate 21 is reached. Flows inward in the radial direction, and further flows in the small diameter cylindrical portion 16 on the left side of the adjacent unit while flowing in the small diameter cylindrical portion 14 on the right side in the axial direction.
As described above, the exhaust gas is circulated in a zigzag manner in the units 1U to 4U constituting the gas passage 6, so that heat exchange with the cooling water flowing through the cooling passage 7 is performed satisfactorily. Become.

Next, a large number of fins 22 extending in the radial direction are provided between the left and right wall portions 13 and 15 of each unit 1U to 4U and the central plate 21 thereof. It can be granted.
That is, as shown in FIG. 3, each fin 22 is formed in a curved shape in which the central portion bulges, and is inclined with respect to the radial direction of the plate 21. When flowing through the space defined by the section 13 (15) and the fins 22, a swirl flow is formed by the fins 22.
The fins 22 are provided on the gas inflow side surface and the discharge side back surface of the plate 21, respectively, and the front surface fins 22 (solid line fins in FIG. 3) and back surface fins 22 (in FIG. 3). The dotted fins) are inclined in opposite directions.

Accordingly, when the exhaust gas circulates radially outward in the space defined by the plate 21, the left wall 15 and the front fins 22, a swirl flow is formed by the fins 22, and the swirl flow is The applied exhaust gas flows in the axial direction while being swung in the circumferential direction on the inner surface of the large-diameter cylinder 12. Then, when the space defined by the plate 21, the right wall 13, and the fins 22 on the back side is circulated inward in the radial direction, a swirl flow in the same direction is formed by the fins 22. become.
As described above, the exhaust gas flowing through the gas passage 6 is swung in one direction by the fins 22 and is circulated in the units 1U to 4U in a zigzag manner as described above, so that good heat exchange is performed. Will come to be.

In the present embodiment, the cooling water flowing through the cooling passage 7 can be given a swirling flow that is opposite to the swirling direction of the exhaust gas flowing through the gas passage 6.
That is, the cooling water inlet port 26 provided at the right end of the casing 2 is disposed at a position away from the axial center of the casing 2 as shown by the solid line in FIG. The cooling water that has flowed in through the casing 2 can be swung along the inner peripheral surface of the casing 2.
On the other hand, the cooling water outlet port 27 provided at the left end of the casing 2 is disposed at a position opposite to the inlet port 26 with respect to the axial center of the casing 2 as indicated by an imaginary line in FIG. Thus, the cooling water flowing in from the inlet port 26 and flowing while turning on the inner peripheral surface of the casing 2 can be smoothly discharged from the outlet port 27.

Further, the cooling water flowing through the cooling passage 7 is also given a swirling flow in the same direction as above by the fins 25 provided on the outer periphery of the large-diameter cylindrical portion 12 constituting each of the units 1U to 4U. It is made to be able to.
That is, on the outer periphery of the large-diameter cylindrical portion 12, a plurality of fins 25 that are inclined with respect to the axial direction of each large-diameter cylindrical portion 12 are provided at equal circumferential positions. Is in close contact with the inner peripheral surface of the casing 2.
The fins 25 are inclined in the same direction. Therefore, the cooling water flowing in from the cooling water inlet port 26 provided at the right end of the casing 2 flows through the cooling passage 7 in the casing 2 in the axial direction. The cooling water that has been swirled by the fins 25 is also discharged to the outside from an outlet port 27 provided at the left end of the casing 2.
Contrary to the above embodiment, the cooling water may flow into the cooling passage 7 from the outlet port 27 and be discharged from the inlet port 26 to the outside.

Next, as described above, the flow path switching valve 9 is integrally connected to the outlet cylindrical member 2e. A bracket 31 is fixed to an outlet side end portion of the outlet cylindrical member 2e, and a housing 32 of the flow path switching valve 9 is fixed to the bracket 31 with a bolt (not shown). A cylindrical bottomed hole 33 is formed in the housing 32 in the vertical direction, and a cylindrical valve body 34 is rotatably fitted in the bottomed hole 33 in a rotatable manner.
The housing 32 is formed with a first inlet port 32a communicating with the bypass passage 5 in the hollow shaft 4, and the right end portion of the hollow shaft 4 is fitted into the left end portion of the first inlet port 32a. is there. The right end portion of the first inlet port 32a opens into the bottomed hole 33, and the valve body 34 is changed by the outer peripheral surface of the valve body 34 as shown in FIG. The right end of one inlet port 32a is sealed so that the bypass passage 5 can be closed.

As shown in FIG. 1, when the valve body 34 is positioned at the first rotation position rotated 90 degrees from the rotation position of the valve body 34 that closes the bypass passage 5, A bypass passage 35 having a circular cross section communicating with the bypass passage 5 is formed.
The bypass passage 35 is formed by penetrating the valve body 34 in the diameter direction of the cylindrical valve body 34 on the same axis as the bypass passage 5 in the hollow shaft 4. When the bypass passage 35 is rotated to the rotational position so as to coincide with the axis of the bypass passage 5 in the hollow shaft 4, the bypass passage 35 can be communicated with the bypass passage 5 in the hollow shaft 4. It is like that.

On the other hand, the housing 32 is formed with two second inlet ports 32b above and below the first inlet port 32a, and the left end of each second inlet port 32b is a tapered communication hole formed in the bracket 31. 36 is communicated with the gas passage 6 of the heat exchanger 3.
The right end portion of each of the second inlet ports 32b opens into the bottomed hole 33, and the valve body 34 connects the bypass passage 35 formed in the valve body 34 to the bypass passage 5 in the hollow shaft 4. In the communicated first rotational position, the right end portion of the second inlet port 32b and hence the gas passage 6 can be closed by the outer peripheral surface of the valve body 34 (FIG. 1).
The valve body 34 is formed with gas passages 37 having two cross-sections that are 90 degrees out of phase with the bypass passage 35 at the upper and lower positions of the bypass passage 35. The valve body 34 can be communicated with the gas passage 6 of the heat exchanger 3 at the second rotational position where the communication between the bypass passage 5 and the bypass passage 35 is blocked (FIG. 2).

Further, an outlet port 32 c is formed in the housing 32, and the outlet port 32 c communicates with both the bypass passage 35 and the gas passage 37 formed in the valve body 34.
The drive shaft 38 fixed to the valve body 34 is interlocked with an actuator (not shown), and the actuator can reciprocate the valve body 34 in a range of 90 °.

In the above configuration, when the exhaust gas temperature at the time of starting the engine is low, the valve element 34 of the flow path switching valve 9 is positioned at the first rotational position shown in FIG. 1 by the actuator. At the same time that the bypass passage 35 of the switching valve 9 communicates with the bypass passage 5 of the EGR cooler 1, the valve body 34 of the passage switching valve 9 closes the gas passage 6 of the heat exchanger 3.
Therefore, the exhaust gas flowing in from the inlet port 8 of the EGR cooler 1 flows through the bypass passage 5 in the hollow shaft 4 and the bypass passage 35 of the flow path switching valve 9 and flows out from the outlet port 32c.
At this time, cooling water flows into the cooling passage 7 of the heat exchanger 3 from the inlet port 26, and the cooling water flows through the cooling passage 7 and flows out from the outlet port 27. Since the gas passage 6 is formed between the passage 5 and the exhaust water flowing through the bypass passage 5 by the cooling water flowing through the cooling passage 7 can be prevented.
Therefore, the temperature of the exhaust gas flowing through the bypass passage 5 after engine startup can be quickly increased.

When the exhaust gas temperature rises, the valve body 34 of the flow path switching valve 9 is rotated by 90 ° by the actuator to be positioned at the second rotational position, and as shown in FIG. Communicates with the gas passage 6 of the EGR cooler 1 and the valve body 34 of the flow path switching valve 9 closes the bypass passage 5 of the EGR cooler 1.
Thus, the exhaust gas flowing in from the inlet port 8 of the EGR cooler 1 flows through the gas passage 6 in the heat exchanger 3 and the gas passage 37 of the flow path switching valve 9 and flows out from the outlet port 32c.
At this time, as described above, the exhaust gas flowing through the gas passage 6 is circulated in a zigzag manner in each of the units 1U to 4U while being swung in one direction by the fins 22, and on the other hand, is circulated through the cooling passage 7. Since the cooling water is also circulated while being swung in one direction by the fins 25, good heat exchange is performed between them.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, a flow path switching valve 9 is integrated in the casing 2 of the EGR cooler 1.
That is, in this embodiment, in order to incorporate the flow path switching valve 9 in the casing 2, the right side of the fourth unit U4 that is the rightmost end is extended in the axial direction as compared with the casing 2 of the first embodiment. The flow path switching valve 9 is incorporated in the extended portion.

The housing 32 of the flow path switching valve 9 in the present embodiment is formed in a thin cup shape as a whole, and the inside thereof has a bottomed hole 33, and a cylindrical valve body 34 is rotatably fitted tightly thereto. ing.
The valve body 34 is configured in the same manner as in the first embodiment to form one bypass passage 35 and two gas passages 37, and a bypass passage is provided on the left side of the housing 32 that serves as an exhaust gas inlet side. A first inlet port 32a that communicates with 35 is formed, and two second inlet ports 32b that communicate with the two gas passages 37 are formed above and below the first inlet port 32a.
Further, an outlet port 32c communicating with both the bypass passage 35 and the gas passage 37 is formed on the right side of the housing 32 serving as the exhaust gas outlet side.

The right end portion of the hollow shaft 4 in which the bypass passage 5 is formed is connected to the outer peripheral surface of the housing 32 in an airtight manner outside the first inlet port 32a formed at the intermediate height position of the housing 32. Thus, the bypass passage 5 in the hollow shaft 4 can be communicated with the bypass passage 35 formed in the valve body 34 through the first inlet port 32a.
On the other hand, the small diameter cylindrical portion 14 on the right side constituting the fourth unit U4 has its right end portion expanded in a conical shape, and the right end portion of the conical portion is positioned outside the two second inlet ports 32b. Thus, the outer peripheral surface of the housing 32 is connected in an airtight manner. Thus, the gas passage 6 in the small-diameter cylindrical portion 14 can be communicated with the gas passage 37 formed in the valve body 34 through the second inlet port 32b.

An outlet cylindrical member 2e is fixed to the closing member 2c that closes the right end portion of the casing 2, and the left end portion of the outlet cylindrical member 2e is outside the outlet port 32c formed in the housing 32. Thus, it is connected to the outer peripheral surface of the housing 32 in an airtight manner.
Other configurations are the same as those of the first embodiment, and the same or corresponding portions are denoted by the same reference numerals as those of the first embodiment.
Even in the second embodiment having such a configuration, it is obvious that the same effects as those in the first embodiment can be obtained. In this embodiment, since the flow path switching valve 9 is incorporated in the housing 2 constituting the EGR cooler 1, it is possible to further reduce the size of the EGR cooler compared to the first embodiment. .

  In each of the above embodiments, the hollow shaft 4 passes through the center position of the cylindrical heat exchanger 3, but the present invention is not limited to this, and the hollow shaft 4 is not connected to the center position of the heat exchanger 3. Of course, it may be provided at an off-center position.

DESCRIPTION OF SYMBOLS 1 EGR cooler 2 Casing 3 Heat exchanger 4 Hollow shaft 5 Bypass passage 6 Gas passage 7 Cooling passage 9 Flow path switching valve 12 Large diameter cylindrical part 13, 15 Wall part 14, 16 Small diameter cylindrical part 20 Connection part 21 Plate 22 25 Fin 32 Housing 34 Valve body 35 Bypass passage 37 Gas passage U1-U4 unit

Claims (7)

A heat exchanger provided in the casing for cooling the exhaust gas; a bypass passage provided in the casing for bypassing the heat exchanger; and an exhaust gas in one of the heat exchanger and the bypass passage. An EGR cooler comprising: a flow path switching valve to be supplied; and the heat exchanger further including a gas passage for circulating the exhaust gas and a cooling passage for cooling the exhaust gas flowing through the gas passage.
A hollow shaft is provided in the casing, the inside of the hollow shaft is used as the bypass passage, the gas passage of the heat exchanger is disposed outside the hollow shaft, and the cooling passage is disposed outside the gas passage. An EGR cooler characterized by that.   The gas passage includes a plurality of large-diameter cylindrical portions and small-diameter cylindrical portions provided coaxially outside the hollow shaft, a wall portion connecting the large-diameter cylindrical portion and the small-diameter cylindrical portion, A plate provided on a hollow shaft and positioned inside each large-diameter cylindrical portion and having a smaller diameter than the large-diameter cylindrical portion and a larger diameter than the small-diameter cylindrical portion. Item 2. An EGR cooler according to Item 1.   A plurality of fins extending radially from the central portion of the plate toward the outer peripheral portion are provided between the plate and the wall portion, and the exhaust gas flowing through the gas passage is separated from the plate by the fins. 3. The EGR cooler according to claim 2, wherein a swirl flow is formed by the fins when flowing between the wall portions.   The fin is provided on each of the exhaust gas inflow side surface and the exhaust side back surface of the plate, and the front surface fin and the back surface fin are inclined in opposite directions, respectively. The EGR cooler according to claim 3.   The large-diameter cylindrical portion, the small-diameter cylindrical portion, the wall portion, the plate, and the fin constitute a set of units, and a plurality of the units are connected to form the gas passage. The EGR cooler according to claim 3 or claim 4.   3. A plurality of fins projecting into a cooling passage are provided on an outer periphery of the large-diameter cylindrical portion, and the cooling water flowing through the cooling passage forms a swirling flow by the fins. The EGR cooler according to claim 5. The flow path switching valve includes a housing, a cylindrical valve body rotatably provided in the housing, and a bypass passage formed in the valve body and capable of communicating with the bypass passage according to a rotational position of the valve body And a gas passage formed in the valve body and capable of communicating with the gas passage according to the rotational position of the valve body,
When the valve body is positioned at the first rotation position, the bypass passage formed in the valve body communicates with the bypass passage in the hollow shaft, and the gas passage formed in the valve body and the above The communication with the gas path of the heat exchanger is interrupted,
When the valve body is positioned at the second rotational position, a gas passage formed in the valve body communicates with a gas passage of the heat exchanger, and a bypass passage formed in the valve body The EGR cooler according to any one of claims 1 to 6, wherein communication with the bypass passage in the hollow shaft is blocked.

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